Expanded metal lath



Sept. 27, 1938.

-E. T. REDDING Er AL 2,131,670

EXPANDED METAL LATH Filed Feb. 20, 1937 LLI Patented Sept. 27, 1938 UNITED STATES PATENT oFFicE l 2,131,670 ExPANnEn METAL mm Edward T. Redding and Arthur V.

Spinosa.

Parkersburg, W. Va., assignors to Penn Metal Company, Inc., Parkersburg, W. Va., a corporation of Delaware Application February 20, 1937, Serial No. 126,924

s claims.

This invention relates to improvements in expanded metal lath, and consists in a novel structary lath machines wherein the opposite edges of f the slitted sheet are gripped by traveling mechanisms and are drawn by the latter along lines diverging in two planes, so that as the lsheet is expanded transversely the strands between the adjoining slits are drawn progressively and uniformly into angular positions. The unbroken edges of the diamond mesh sheet upon which the aforesaid mechanisms operate and from which the expansion occurs are known as the selvage edges, as distinct from the edges at the other sides or ends of the sheet which exhibit the extremities of the severed strands.

Heretofore in the manufacture of this type of diamond metal lath, it has been the conventional and universal practice to so initially slit the metal sheet from which the mesh is formed that the strands at the selvage edges are of materially greater width than the strands in the intermediate portion of the sheet. We have discovered that the characteristics of metal lath of this type may be materially improved by forming the selvage strands of the same width, or substantially so, as the other strands of the lath, and that the advantages inherent in this construction considerably outweigh any other advantages attributable to the prior conventional selvage formation.

One point of disadvantage of this type of metal lath as heretofore constructed has arisen from the fact that the sheets of metal lath when placed in a wall or ceiling structure must be overlapped at the edges, with the result that in the overlapped areas and by reason of the multiple thickness of lath, the at continuity of the plaster-receiving surface is destroyed. This departure from the desirable plane surface is particularly marked within those areas where three or four of the metal lath sheets form a juncture. It is highly important from the plasterers viewpoint that the base to.

which the plaster is applied shall present an absolutely plane face, since any substantial irregularities or departures from the plane materially complicate the production of a flat plaster surface and preclude uniformity of thickness in the plaster coating. In producing the required abso- (Cl. 'Z2-117) lutely plane plaster surface on a ceiling or partition, the work of the plasterer is materially complicated by any departure 'from the plane in the plaster base, such for example as that which necessarily occurs at the juncture of two or more sheets of the conventional metal lath. It is obvious that any projections or inequalities in the surface of the plaster base require an unequal distribution of mortar over the base'in order tol obtain the plane plaster surface. Such complications necessarily add to the cost of the plasterers work. It is apparent also that on a base presenting surface inequalities or protrusions, the

production of a plaster coating of given minimum thickness requires the use of larger amounts or a. plane surface. In addition to these factors affecting labor and costs, the differences orvariations in the thickness .of the plaster coating on a ceiling or partition arising from irregularities existing in the plaster base tends tov weaken the plaster structure, since it produces areas of maximum Weakness in which theeffects of the stresses set up within 'the plaster tend to concentrate with the production in those areas of relatively large cracks, instead of said stresses, as in walls of .uniform thickness, being distributed over the entire wall area and being manifested merely by minuteinvisible hair cracks. Also any undue bulk of metal in any one area of a wall surface, particularly one associated with an abnormally small plaster thickness at that point, tends-to introduce condensation stains which produce v'streaks orv discolorations. Such condensation streaks, quite commonly found in ceilings and walls employing wood joists and lath, are not entirely'elminated by the use of the prior conventional metal lath by reason of the necessity for lapping the edges ofr ventional metal lath of thisy class as outlined above may be eliminated to a substantial degree by the provision of a lath wherein preferably the thickness of the individual strands is reduced to a minimum and wherein further the metal strands inclusive of the selvage strands are substantially of uniform width throughout the sheet.

Iii plaster than will be required by a base presenting This will be more readily understood by reference to the attached drawing, in which:

Figure 1 is a view in perspective of a fragment of a sheet of metal lath incorporating our invention;

Fig. 2 is a corresponding view of a section of metal lath of the conventional form and as unlversally produced prior to our invention;

Fig. 3 is a section on the line 3 3, Fig. 1;

Fig. 4 is a section on the line 4 4, Fig. 2;

Fig. 5 is a fragmentary sectional view illustrating an overlapped juncture of two sheets of metal lath as it may occur in a wall structure, and

Fig. 6 is a view corresponding to that of Fig. 5 and showing for the purpose of comparison a corresponding juncture between sheets of -metal lath of the prior conventional form.

Referring to Figs. 1 and 3, it will be noted that the metal strands I which dene the sides of the diamond-shaped openings of the lath are substantially of uniform width throughout the sheet, and that the strands la at the selvage edge of the sheet are of substantially the same width as the intermediate strands l. It will be noted further, by reason of the peculiar formation of the expanded metal sheet, that those portions of the metal which form the junctures between the various strands occupy positions in planes either normal to theplane of the sheet or slightly inclined from this plane, and that accordingly the effective thickness of the lath is determined by the width or height of these junctures where the individual strands come together, and hence indirectly by the width of the individual' strands. Where as shown in Figs. 1 and 3 the metal strands inclusive of theselvage strands la are of uniform width or substantially so, the effective thickness at the selvage edge is no greater than the effective thickness in other parts of the sheet. Tri-the conventional lath of this type, as illustrated in Figs.

y2 and 4, andl in accordance with the priorY practice, the selvage strand 2a has a width materially in excess of that of the intermediate strands 2, usually more than twice as great, and as a result the effective thickness of the sheet along the selvage edges is correspondingly greater than the effectivethickness of the other portionsof the sheet.-

In Figs. 5 and 6 we have illustrated a condition existing in a ceiling or wall structure employing metal lath of the type to which our invention relates. In each of these drawings the reference numeral 3 indicates a stud in the form of a. channel bar to which the sheets of metal lath, I and 5 in Fig. 5, and 4a and 5a in Fig. 6, are secured by means of wire clips 6. The sheets of lath shown in Fig. 5 are made in accordance with our invention, 'being of substantially uniform effective thickness throughout, whereas the sheets shown in Fig. 6 are made in accordance with the prior conventional practice and exhibit an effective thickness at the selvage edges materially in excess of the effective thickness of the other portions of the lath. It will be apparentv that in the assembly shown in Fig. 5 the effective thickness of the lath in that portion of the structure in which the sheets are overlapped isapproximately twice the effective thickness of the individual sheets. In the assembly illustrated in Fig. 6, however, the effective thickness of the lath in the overlapped area is materially in excess of twice the normal effective thickness of the lath sheets, and this increase in thickness in the overlapped areas is due entirely to the extra width of the selvage strands 2a. The illustrations of both 'diamond-shaped openings without,

Figs. 5 and 6 have been somewhat exaggerated for the purpose of.' clarity, but it has been found in practice that with sheets of lath made in accordance with our invention the maximum thickness in an overlapped area is materially less than twice the maximum effective thicknesses of the individual sheets, this being due to the uniformity in the width of the strands in the overlapped areas and the consequent ability of these strands to mesh or interseat more or less accurately and closely. In the absence of this uniformity of strand width and with a selvage strand of extra width, the ability of the superimposed sheets to interseat in the manner described is prevented, so that the.thickness of overlapped portions of sheets of conventional form is again relatively great.

In the manufacture of metal lath of this type, it is customary to form the sheets from slitted blanks of eight inch Width, the width of the expanded sheet being twenty-four inches. There has been a tendency toward reduction in the width of the strands for the purpose of decreasing the size and increasing the number of the however, affecting the unit area weight of the lath. Relatively small openings have been found to facilitate the plastering operation. With this reduction in the Width of the intermediate strands, however, there has been no corresponding reduction in the width of the selvage strands. In the conventional lath of this type, it is customary to provide a selvage strand approximately .13 of an inch in width, and this average Width of selvage strand has remained unchanged in spite of reduction in the width of the intermediate strands.` "As previously set forth, the width of the strands in a lath of this character determines the effective thickness of the sheet, and it is apparent, therefore, that in addition to increasing the number and size of the diamond openings, reduction in the width of the metal strands will also necessarily have the effect of reducing the effective thickness of the lath sheet. Such reduction in sheet thickness, if full advantage were taken, would obviously aid in reducing the undesirable bulk of overlapped joints such as shown in Figs. 5 and 6. Reduction in the width of the intermediate metal strands with'- out reduction in the width of the selvage strands, however,4 affords little or no advantage in this respect, and on the other hand tends to accentuate .the irregularities appearing in wall assemblies where the lath sheets overlap. It is apparent that by reducing the width of the strands to a practical minimum, say .05 of an inch and at the same time forming the selvage strands in accordance with our invention of substantially the same width as the intermediate strands, a lath is produced of definitely improved characteristics in its ability to form lapped joints in a wall structure withrelatively little departure from the desirable plane surface condition.

' We claim:

1. An improved metal lath of the deployed diamond type wherein the effective thickness of the lath sheet is determined by the width of the metal strands defining the diamond apertures, said lath being characterized by substantial uniformity of strand and selvage width and lath sheet is determined by the width of the lath sheet is determined by the width of the metal strands defining the diamond apertures, said lath exhibiting throughout a substantially uniform strand and selvage width of approximately .05" and having a substantially uniform 5 effective sheet thickness o1' approximately .10".

ARTHUR V. SPINOSA. EDWARD T. REDDING, 

